make shell scripts respect PATH

use the bash from PATH, not from /bin

fixes #141

top1m/make_ca_files.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 if [[ ${1,,} == "-h" ]] || [[ ${1,,} == "-help" ]] || \
     [[ ${1,,} == "-help" ]] || [[ ${#} -lt 1 ]]; then

top1m/make_ca_trusted.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 if [[ ${1,,} == "-h" ]] || [[ ${1,,} == "-help" ]] || \
     [[ ${1,,} == "--help" ]]; then

top1m/process-certificate-statistics.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 if [ ! -d ./ca_files ]; then
     echo "Directory with collected CA certificates missing!" >&2